how to fix P0301 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, fuel pressure gauge, multimeter.
• Ensure the vehicle is parked on a level surface and the engine is cool. Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 1 using a socket set.
• Remove the spark plug using a spark plug socket. Inspect the spark plug for fouling or damage.
• If the spark plug is worn, clean or replace it with a new one, ensuring it matches the manufacturer's specifications (typically NGK or Denso for Toyota).
• Reinstall the spark plug and torque to the manufacturer's specifications (usually around 13-16 ft-lbs).

3. Check and Replace Ignition Coil

• If the spark plug is in good condition, proceed to inspect the ignition coil for cylinder 1.
• Use a multimeter to check the coil's resistance according to the specifications (usually around 0.4 to 0.5 ohms for primary resistance).
• If the ignition coil is defective, replace it with a new coil. Ensure it is seated properly and reconnect the connector.

4. Inspect Fuel Injector

• If misfire persists, check the fuel injector for cylinder 1.
• Remove the fuel injector connector and use a multimeter to verify proper operation (check for resistance, typically around 12-16 ohms).
• If the injector is faulty, replace it with a new one, ensuring proper sealing upon installation.

5. Verify Cylinder Compression

• If the issue remains unresolved, perform a compression test on cylinder 1.
• Remove the spark plug and connect the compression tester to the spark plug hole.
• Crank the engine and note the compression reading. It should be within the manufacturer's specified range (usually around 180-200 psi).
• If compression is low, further investigation into the cylinder head, piston rings, or valves may be necessary.